For my particular application... I've got a 2004 Grady White 228 Seafarer with an F225 Yamaha outboard on it but I can't find performance data with an F225 anymore, so I used a 228 Seafarer with an F250 instead. On the Sharrow Marine website they claim that the single blade prop will be "As much as 30% more efficient between 2500-4000 RPM". A brand new, well before they discontinued them, 228 Seafarer with an F250 Yamaha on it and a normal prop will run at 4,000 rpm and burn 11.5 gph as well as 2.91 mpg. With the Sharrow brand prop being "As much as 30% more efficient between 2500-4000 RPM" that would put you at around 8.05 gph burned and 3.783 mpg. At a price tag of $4,900 for the propeller and say $4/gal for gasoline, you're saving roughly 3.45 gph at 4,000 rpm x $4/gal for gasoline, which equals $13.80 worth of fuel that you save. If you divide the $13.80 savings over a one hour period by the hefty price tag of $4,900 you're looking at what... 355 hours of using the Sharrow prop before you'd even break even, if my math is correct?
And that's if the "30%" claim is even all that accurate, which I'm sure if those are the actual results, that they were done with perfect weather and sea conditions to get the best numbers possible. I'm all for saving money on fuel and getting as good of fuel economy as possible, yet I can't drop $5k on a propeller to start to break even after 355 hours of usage. If I started breaking even, or maybe even being ahead after a season... well then it might be a different story. But for the price and amount of time it'll take to make that $5k back, I simply can't justify it and would much rather put that money elsewhere into better things like new electronics, fuel, insurance, tabs and so on. At $4/gal, $5k will get you exactly 1,250 gallons of fuel. That's a good deal of fuel to burn without blowing it on a prop that you likely won't see all of the benefits that they claim you'll see.